1. Field of the Invention (Technical Field)
The present invention relates to apparatus for generating electricity from the movement of flowing fluids, and thus is related generally to windmill and water mill devices, and more particularly relates to an apparatus for generating electricity from aeolian oscillations due to ocean tides or wind.
2. Background Art
Windmills and water mills have been used for centuries to harness the kinetic energy of wind and flowing water. Historically, most wind and water mills have involved devices incorporating fins or paddles. The fins or paddles are disposed mostly normal to the direction of wind or water stream flow, and upon some type of an axle, with the result that the force of the wind or water flow impinging against the fins or paddles induces a rotary motion of the axle. The rotating axle is then connected to some additional device for accomplishing work, such as a pump, electrical generator, millstone, or the like. More recently, the use of sophisticated turbines, particularly in hydroelectric dams, has permitted more efficient harnessing of wind or water flow. Even highly developed turbines, however, tap the force generated by a flowing fluid driving a paddle- or propeller-like device to cause rotary motion.
With energy demands increasing worldwide, there is a rising need for an apparatus for generating power from naturally occurring fluid flow, There is a special need for a system that can harness wind or water flow in areas of marginal potential for efficient energy production, e.g. areas of mild or only moderate winds, or locations of relatively slow water flow velocities (such as deep ocean tidal flows). A shortcoming of many known devices for harnessing natural fluid flow is their fundamental reliance upon conventional "paddle" or "fin" devices for converting linear fluid flow into rotary mechanical motion. The use of fins and paddles to create rotary motion, for generators and the like, limits the locations where these known devices may be deployed, as rotary devices generally require comparatively high wind or water flow velocities.
It has been known for at least a century that a generally cylindrical object, such as a wire disposed in tension between two anchors, will vibrate or oscillate if placed in a moving fluid, such as the wind, due to the effect of the fluid flowing past and around the object. Particularly in the case of objects oscillating in the flow of rushing wind, the phenomenon has been referred to as "aeolian oscillation." Aeolian oscillation refers generally to the oscillation of an object, typically but not necessarily an object having a cylindrical cross section, caused by the movement there past of a flowing fluid such as air (wind) or water. Experiments reported in the late 1800's by J. W. Rayleigh involved moving various diameter wires through air while measuring the aeolian tone frequencies generated by the vibrating wire. It was empirically demonstrated that a cylindrical object will oscillate at a frequency N in wind moving at velocity V according to the formula ##EQU1## where N is in cycles per second and the constant 5 is satisfied for wind velocity V and wire diameter d in the centimeter-grams-seconds system of units. Using the formula, wire-stringed wind harps may be designed to produce tones at certain pitches at particular wind velocities.
An advantage of aeolian oscillation is that oscillation can be induced at relatively low fluid flow velocities. An aeolian oscillation of significant magnitude can be generated in a wind too mild to turn a conventional windmill.
Against the foregoing background, the present invention was developed to harness the kinetic energy of a flowing fluid, whereby aeolian oscillatory motion is converted into electrical energy. The only previous effort, of which this applicant is aware, to harness the energy of aeolian oscillation is the device described in U.S. Pat. No. 4,024,409 to Payne.